Semiconductor Devices

Abstract

To provide a power conversion device in which heat dissipation, vibration resistance, connection reliability, and insulation reliability are improved.SOLUTION: A power conversion device comprises: a semiconductor device that includes a semiconductor element, two heat spreaders, and an external terminal; a circuit board that includes a first insulation layer; and a cooler. The circuit board includes: a concave part in which the semiconductor device is installed; a first conductive layer that forms a bottom surface of the concave part; and a second conductive layer that is arranged in a layer different from the first conductive layer, and of which at least one part is exposed in the concave part. One of the heat spreaders is in contact with the bottom surface of the concave part, and is bonded to the first conductive layer via a first metal bonding material. The external terminal is bonded to the second conductive layer via a second metal bonding material. The other of the heat spreaders is in pressure-contact with the cooler via a second insulation layer different from the first insulation layer.SELECTED DRAWING: Figure 2A

Description

[Technical Field]

[0001] The present invention relates to a semiconductor device. [Background technology]

[0002] Power conversion devices using power semiconductor elements are widely used in fields such as consumer, automotive, railway, industrial, and infrastructure applications. For example, automotive power semiconductor elements are used in electric vehicles (EVs) driven by motors and hybrid vehicles (HEVs) that combine motor and engine drive. In these EVs and HEVs, the battery's DC voltage is converted into a pseudo-AC voltage by switching the power semiconductor elements, driving the motor with high efficiency. In power conversion devices equipped with these power semiconductor elements, it is necessary to mount high-voltage circuit components on printed circuit boards in a way that does not impair reliability.

[0003] Patent Document 1 discloses the configuration of an electrical device in which a recess is formed in the thickness direction of a printed circuit board, high-voltage circuit components are placed in the recess, and an insulating material is filled in the recess, thereby ensuring the insulation of the high-voltage components and preventing an increase in the number of components and manufacturing steps involved in applying the insulating material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-77744 Summary of the Invention [Problem to be solved by the invention]

[0005] When the heat generation amount of a power module equipped with electronic components increases, the heat needs to be dissipated to a cooler. However, in conventional configurations, depending on the installation conditions of the power module mounted on the board, the heat dissipation performance may decrease, which may result in a decrease in the reliability of the entire device. In view of this, an object of the present invention is to provide a power conversion device with improved heat dissipation performance, vibration resistance, connection reliability, and insulation reliability. [Means for solving the problem]

[0006] The power conversion device of the present invention includes a semiconductor device having a semiconductor element, two heat spreaders joined to both sides of the semiconductor element on one side thereof, and external terminals, the semiconductor device being sealed with insulating resin so that the other sides of the two heat spreaders and parts of the external terminals are exposed, a circuit board on which the semiconductor device is mounted and having a first insulating layer, and a cooler for cooling the semiconductor device, the circuit board having a recess in which the semiconductor device is placed, a first conductor layer forming a bottom surface of the recess, and a heat spreader formed on the first conductor layer. and a second conductor layer disposed on a different layer and at least a portion of which is exposed in the recess, wherein one of the two heat spreaders is in contact with the bottom surface of the recess on the other side and is joined to the first conductor layer via a first metal bonding material, the external terminal is joined to the second conductor layer via a second metal bonding material, and the other of the two heat spreaders is pressed against the cooler on the other side via a second insulating layer different from the first insulating layer. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a power converter with improved heat dissipation performance, vibration resistance, connection reliability, and insulation reliability. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view of a conventional power conversion device. [Figure 2A] 1 is a diagram showing a cross-sectional structure of an embodiment of a power conversion device of the present invention; [Figure 2B] 1 is a diagram showing a cross-sectional structure of a semiconductor device; [Figure 3] 1 is a diagram showing a cross-sectional structure of an embodiment of a power conversion device of the present invention; [Figure 4] 1 is a diagram showing a cross-sectional structure of an embodiment of a power conversion device of the present invention; [Figure 5] 10A to 10C are cross-sectional views of the circuit board illustrating a step of forming a first conductor layer. [Figure 6] 4 is a cross-sectional view of a circuit board illustrating a step of forming a first conductor layer according to an embodiment of the power conversion device of the present invention. FIG.

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and some omissions and simplifications have been made as appropriate for clarity of explanation. The present invention can be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

[0010] In order to facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

[0011] (Conventional configuration) (Figure 1) An electronic component 10 provided in a power conversion device has external terminals 15 for connection with circuit conductors 22 of a circuit board 20. To protect the circuit pattern including the circuit conductors 22, a solder resist 23, which is an insulating film, is provided on the entire surface of the circuit board 20.

[0012] When electronic component 10 is a precision device such as a power module (semiconductor device) equipped with a power semiconductor element (hereinafter referred to as a semiconductor element), it needs to be protected with an insulating resin on circuit board 20. To this end, a recess 24 is formed in circuit board 20, electronic component 10 is placed inside recess 24, and insulating resin filler 33 is filled between recess 24 and electronic component 10. In addition, a cooler 41 having a water channel 42 is placed on the opposite side of the bottom surface of recess 24 (insulating layer 21 of circuit board 20) with the electronic component 10 in between. This achieves a power conversion device that achieves both stability and heat dissipation of electronic component 10, improving reliability.

[0013] However, for example, if the solder paste used for joining is not consistent when placing the power module in the recess 24, it may be misaligned or tilted relative to the circuit board 20, which could make it impossible to maintain reliable electrical connection and stability.

[0014] (Power conversion device according to one embodiment of the present invention) (Figure 2A, Figure 2B) The basic structure of the power converter will be described. The power converter 100 is composed of a power module (semiconductor device 10) including a semiconductor element 11 such as an IGBT (Insulated Gate Bipolar Transistor), a printed circuit board 20, a cooler 41, bus bars, capacitors, and other components (not shown). While FIG. 2A shows an example in which the power converter 100 has two semiconductor devices 10 mounted on the circuit board 20, the number of semiconductor devices 10 is not limited to two and can be any number. In the power converter 100, the semiconductor device 10 generates heat due to the switching of a large current in the semiconductor element 11. Furthermore, the circuit board 20, bus bars, capacitors, and other components also generate heat in proportion to the product of the squares of the currents flowing through them due to losses caused by the electrical resistance components of each material. The cooler 41 cools these heat-generating components.

[0015] A power conversion device 100 equipped with such a structure is installed in an HEV or EV. While an HEV runs on the driving force of an engine supplemented by the driving force of a motor, an EV runs purely on the driving force of a motor, which is electric power, and therefore the power conversion device 100 is required to be able to handle larger amounts of power. When the current is increased, loss increases in proportion to the square of the current, and the amount of heat generated increases. Therefore, to reduce heat generation, it is necessary to increase the amount of conductor used in the power conversion device 100 and reduce the conductor resistance. As a result, the volume and weight of the power conversion device 100 increase, causing it to become larger. Furthermore, because extending the driving range is an issue for EVs, it is necessary to increase the capacity of the battery installed, and therefore there is a demand for a smaller and lighter power conversion device 100.

[0016] The semiconductor device 10 will now be described. Heat spreaders 12 and 13 are bonded to both sides of a semiconductor element 11 via solder (not shown), and the semiconductor element 11 (its control terminal) is electrically bonded to an external terminal 15 using wires 14. With the heat spreaders 12 and 13 exposed on the side opposite to the side bonded to the semiconductor element 11 and with the external terminal 15 partially exposed, the semiconductor device 10 is sealed by transfer molding with insulating resin 16.

[0017] The semiconductor device 10 is electrically connected by bonding heat spreaders 12 and 13 to both sides of the semiconductor element 11, and is also provided with external terminals 15 for electrically connecting the semiconductor element 11 to the circuit board 20. The other side of the heat spreader 12, which is not bonded to the semiconductor element 11, is connected to the bottom surface of a recess 24 provided in the circuit board 20, and the other side of the heat spreader 13, which is not bonded to the semiconductor element 11, is connected to a cooler 41. The semiconductor element 11 is, for example, an IGBT, and the heat spreader 12, which is connected to the collector electrode side, is bonded to the bottom surface of the recess 24.

[0018] In the circuit board 20 on which the semiconductor device 10 is mounted, a first metal bonding material 31 is disposed on a first conductor layer 25 provided on the bottom surface of the recess 24. The first metal bonding material 31 is, for example, a solder sheet. In addition, a second metal bonding material 32 is applied to a second conductor layer 26, which is a board wiring layer one step higher above the first conductor layer 25 in the drawing and is partially exposed at a step provided in the recess 24. The second metal bonding material is, for example, a solder paste. This allows the external terminals 15 of the semiconductor device 10 to be bonded to the second conductor layer 26 of the circuit board 20 over a short distance without bending, thereby reducing the main circuit inductance.

[0019] Furthermore, by making the outer shape of the first conductor layer 25 larger than the outer shape of the heat spreader 12 of the semiconductor device 100 to which it is bonded via the first metal bonding material 31, the first conductor layer 25 can more efficiently spread heat from the semiconductor element 11, thereby improving heat dissipation performance.

[0020] Although the first metal bonding material 31 and the second metal bonding material 32 are applied using the same solder material, different materials may be used for each material as long as there are no problems with electrical connection and stability of the semiconductor device 100.

[0021] The semiconductor device 10 is mounted in the recess 24 so that the external terminals 15 are connected to the second conductor layer 26. A reflow device (not shown) melts and solidifies the first metal bonding material 31 and the second metal bonding material 32, respectively, thereby bonding the first conductor layer 25 to the heat spreader 12 and bonding the second conductor layer 26 to the external terminals 15. This fixes the semiconductor device 10 in the recess 24. The gap between the semiconductor device 10 fixed in the reflow device and the recess 24 is filled with a resin filler 33, which is then cured at a predetermined temperature. This ensures high insulation reliability even when a high voltage is applied.

[0022] Cooler 41 presses against semiconductor device 10 from both above and below, and an insulating layer 43, which is a high-thermal-conductivity insulating sheet made of a mixture of inorganic filler and epoxy resin and has high thermal conductivity, is attached to the pressing surface. Furthermore, an electrically insulating heat dissipating material 44 is applied to insulating layer 43. Note that instead of a high-thermal-conductivity resin sheet, a ceramic plate such as aluminum nitride or silicon nitride may be used for insulating layer 43.

[0023] The cooler 41 is pressed against the semiconductor device 10 placed in the recess 24 of the circuit board 20 from the opening side of the recess 24 via the insulating layer 43 and the electrically insulating heat dissipation material 44. On the other hand, the cooler 41 is also pressed against the outer surface of the bottom surface of the recess 24, and the double-sided cooling cooler 41 improves heat dissipation of the semiconductor device 10.

[0024] With this configuration, heat generated by the semiconductor element 11 is transferred through the heat spreaders 12 and 13 bonded to the semiconductor element 11, and then through the insulating resin 16 and the metal bonding materials 31 and 32, which have lower thermal resistance than the insulating layer 21 of the circuit board 20, to the first conductor layer 25, which forms the bottom surface of the recess 24 of the circuit board 20. The heat that reaches the first conductor layer 25 is dissipated from the outer surface of the circuit board 20 on which the recess 24 is formed to the cooler 41, which is pressure-bonded to the circuit board 20 via an insulating layer 43 different from the insulating layer 21 of the circuit board 20, thereby improving the heat dissipation performance of the semiconductor device 10. Furthermore, as will be described later with reference to FIG. 3 , if the semiconductor device 10 is tilted during installation, the metal bonding material 31 absorbs the tilt, maintaining the reliability of the device 10 without degrading its heat dissipation performance. This also contributes to miniaturization by preventing unnecessary increases in size.

[0025] Furthermore, since the heat spreader 12 is bonded to the first conductor layer 25 via the first metal bonding material 31, the bonding area between the semiconductor device 10 and the circuit board 20 can be increased compared to when the external terminals 15 of the semiconductor device 10 are metal-bonded only to the second conductor layer 26 of the circuit board 20, thereby improving vibration resistance and connection reliability.

[0026] (Figure 3) In the power conversion device 100, even if the semiconductor device 10 is mounted at an angle relative to the circuit board 20, the first metal bonding material 31 absorbs the angle of the semiconductor device 10, thereby maintaining the reliability of the semiconductor device 10.

[0027] (Figure 4) In the power conversion device 100, providing a recess 24 on the circuit board 20 carrying the semiconductor device 10 can cause warping of the entire board, potentially resulting in defects. Therefore, the first conductor layer 25 of the circuit board 20 is made of thick copper, and accordingly, the conductor layer on the opposite side of the circuit board 20 is made of thick copper circuit conductor 27. This reduces warping of the entire circuit board 20 and semiconductor device 10, improving heat dissipation without impairing the reliability of the device. In this configuration, both the first conductor layer 25 and the thick copper circuit conductor 27 are 1 mm thick.

[0028] (Substrate manufacturing method) (Figure 5) First, as shown in Figure 5(a), a multilayer printed circuit board having four conductor layers 22 is prepared for circuit board 20. Since the current handled by the power conversion device is several hundred amperes (A), 500 µm of copper foil is used for conductor layer 22 of circuit board 20, which is thicker than the copper foil generally used in electronic devices. Furthermore, a glass fiber reinforced epoxy resin base material is used for insulating layer 21 of circuit board 20. Each conductor layer 22 of circuit board 20 is formed in advance by etching copper foil so as to become a circuit for the power conversion device.

[0029] Next, in FIG. 5(b), a recess 24a was formed by countersinking the portion of the circuit board 20 where the semiconductor device was to be placed, up to a position where the surface of the third conductor layer from the top (the second conductor layer 26 described above) was visible.

[0030] 5(c), a recess 24b is formed by similar countersinking to the recess 24a formed in FIG. 5(b), leaving a portion of the second conductor layer 26 exposed, and extending from the top to a position where the surface of the fourth conductor layer (first conductor layer 25) is visible. This forms a recess 24 in the circuit board 20.

[0031] (Figure 6) A method for manufacturing a circuit board 20 having a first conductor layer 25 made of thick copper as described in FIG. 4 will be described. The circuit board 20 is manufactured by a method different from the method described in FIG. 5. First, as shown in FIG. 6(a), a multilayer printed circuit board having four conductor layers 22 is prepared as the circuit board 20. The current to be handled, the material of the conductor layers, the material of the insulating layers, and the formation of the conductor layers of the circuit board 20 are the same as those in FIG. 5.

[0032] Next, in FIG. 6(b), a recess 24a was formed by countersinking the portion of the circuit board 20 where the semiconductor device 10 would be placed, extending from the top to a position where the surface of the third conductor layer (second conductor layer 26) was visible. In FIG. 6(c), a recess 24b was formed, leaving a portion of the second conductor layer 26 exposed and opening so that the circuit board 20 could penetrate through it. In FIG. 6(d), a 1 mm thick copper plate, different from the copper foil of the conductor layer 22 of the circuit board 20, was bonded to the bottom side of the recess 24b of the circuit board 20 using adhesive 28 in the recess 24b formed in FIG. 6(c), thereby forming a first conductor layer 25 and completing the recess 24 of the circuit board 20. Note that the first conductor layer 25 is formed so as to partially overlap the second conductor layer 26 in the thickness direction of the circuit board 20, from the viewpoint of achieving both heat dissipation properties of the semiconductor device 10 and reduced inductance by bonding the second conductor layer 26 and external terminals 15 closely together.

[0033] By doing this, the thickness of the first conductor layer 25 is not affected by manufacturing constraints of the circuit board 20, so a thicker conductor layer 25 can be formed as required, thereby improving heat dissipation performance.

[0034] According to the embodiment of the present invention described above, the following advantageous effects are achieved.

[0035] (1) A power conversion device 100 includes a semiconductor device 10 having a semiconductor element 11, two heat spreaders 12 and 13 bonded to one side of each of both sides of the semiconductor element 11, and an external terminal 15, and sealed with insulating resin 16 so that the other sides of the two heat spreaders 12 and 13 and a portion of the external terminal 15 are exposed, a circuit board 20 on which the semiconductor device 10 is mounted and has a first insulating layer 21, and a cooler for cooling the semiconductor device 10. The circuit board 20 has a recess 24 in which the semiconductor device 10 is placed, a first conductor layer 25 forming the bottom surface of the recess 24, and a second conductor layer 26 disposed on a layer different from the first conductor layer 25 and at least a portion of which is exposed in the recess 24. One heat spreader 12 of the two heat spreaders 12, 13 has the other surface in contact with the bottom surface of recess 24 and is bonded to first conductor layer 25 via first metal bonding material 31, external terminal 15 is bonded to second conductor layer 26 via second metal bonding material 32, and the other surface of the other heat spreader 13 of the two heat spreaders 12, 13 is pressure-bonded to cooler 41 via second insulating layer 43 different from first insulating layer 21. In this way, it is possible to provide a power conversion device 100 with improved heat dissipation performance, vibration resistance, connection reliability, and insulation reliability.

[0036] (2) The first conductor layer 25 is formed so that a portion thereof overlaps with the second conductor layer 26 in the thickness direction of the circuit board 20. This allows the power converter 100 to achieve both good heat dissipation and reduced inductance.

[0037] (3) The first conductor layer 25 has an outer shape larger than the outer shape of the other surface of the heat spreader 12 exposed from the insulating resin 16. This can improve the heat dissipation performance of the power conversion device 100.

[0038] (4) An insulating resin filler 33 is filled between the recess 24 and the semiconductor device 10. This allows the power conversion device 100 to achieve high insulation reliability even when a high voltage is applied.

[0039] (5) The first metal bonding material 31 and the second metal bonding material 32 have the same composition. This allows the productivity of the power conversion device 100 to be improved.

[0040] (6) The semiconductor element 11 is an IGBT, and the heat spreader 12 on the collector electrode side of the IGBT is joined to the bottom surface of the recess 24. This can improve the heat dissipation of the power conversion device 100 that uses the IGBT.

[0041] (7) The circuit board 20 employs a manufacturing method in which a circuit board 20 having a plurality of conductor layers 22 is prepared, an opening is formed in the circuit board 20 down to the surface of a certain conductor layer 22, and a countersink is performed so as to penetrate from the inner periphery of the surface of the certain conductor layer 22 to the opposite side of the circuit board 20, thereby forming an opening in the circuit board 20, and a copper plate is bonded to the opening, thereby forming a recess 24 in the circuit board 20. In this way, the circuit board 20 is not affected by manufacturing constraints, and a thicker conductor layer 25 can be formed as required, thereby improving heat dissipation performance.

[0042] The present invention is not limited to the above-described embodiments, and various modifications and combinations of other configurations are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to those having all of the configurations described in the above-described embodiments, and includes those in which some of the configurations are omitted. [Explanation of symbols]

[0043] 10: Electronic components (semiconductor devices) 11: Power semiconductor element 12: Heat spreader (collector side of IGBT) 13: Heat spreader (emitter side of IGBT) 14: Wire 15: External terminal 16: Insulating resin 20: Circuit board 21: Insulating layer of circuit board 22: Circuit conductor of circuit board 23: Solder resist 24: Recessed portion of circuit board 24a: First recess 24b: Second recess 25: First conductor layer 26: Second conductor layer 27: Thick copper circuit conductor 28: Adhesive 31: First metal bonding material 32: Second metal bonding material 33: Resin filler 41:Cooler 42: Cooler waterway 43: Cooler insulation layer 44: Electrically insulating heat dissipating material 100: Power conversion device

Claims

1. a semiconductor device including a semiconductor element, two heat spreaders bonded to both surfaces of the semiconductor element on one side thereof, and external terminals, the semiconductor device being sealed with insulating resin so that the other sides of the two heat spreaders and portions of the external terminals are exposed; a circuit board on which the semiconductor device is mounted and which has a first insulating layer; a cooler for cooling the semiconductor device, the circuit board has a recess in which the semiconductor device is placed, a first conductor layer forming a bottom surface of the recess, a second conductor layer disposed on a layer different from the first conductor layer and at least a portion of which is exposed in the recess, and a third conductor layer formed on a surface opposite to a surface on which the first conductor layer is formed; one of the two heat spreaders is in contact with the bottom surface of the recess with the other surface thereof and is joined to the first conductor layer via a first metal joining material; the external terminal is joined to the second conductor layer via a second metal joining material; the other of the two heat spreaders is pressure-welded to the cooler on the other surface thereof via a second insulating layer different from the first insulating layer; The thickness of the first conductor layer and the thickness of the third conductor layer are greater than the thickness of the second conductor layer. Power conversion device.

2. The power conversion device according to claim 1, The first conductor layer is formed so that a portion thereof overlaps with the second conductor layer in the thickness direction of the circuit board. Power conversion device.

3. The power conversion device according to claim 1, The first conductor layer has an outer shape larger than an outer shape of the other surface of the heat spreader exposed from the insulating resin. Power conversion device.

4. The power conversion device according to claim 1, An insulating resin filler is filled between the recess and the semiconductor device. Power conversion device.

5. The power conversion device according to claim 1, The first metal bonding material and the second metal bonding material have the same composition. Power conversion device.

6. The power conversion device according to any one of claims 1 to 5, The semiconductor element is an IGBT, and the heat spreader on the collector electrode side of the IGBT is joined to the bottom surface of the recess. Power conversion device.

Images